1990 Bayliner Trophy with twin Force 120s need advice on prop sizes

[gica]

It has 4 blade Turning Point 13x19 on right now and it only reaches 4100 RPMs on the dash could be more or less on a digital gauge. I read some and it is mentioned that 13.5x17 or 13.5x15 if heavy load is the way to go. This boat is heavy at least 3500Lbs maybe more. I am going to fish it on the SoCal west coast offshore waters, 3-4 people and fish tank. Really appreciate the help.

 

[gica]

Do on the boat there are 2 props 4 blades 14 by 19 I will show pics.
The guy replaced 2 older 3 blade props and the only marking is a number 21 on them.
There is also a 3 blade white prop that has 13.5x15-k on it.

 

[Texasmark]

First thing is to get loaded up and go out and firewall the throttles and trim to best performance. What is the RPM of both engines under these conditions? Best performance is near the top end of the recommended operational RPM range.....would be somewhere around 5500 to 6000 RPM.
If you are running around 4500 or below you are way over propped....too much pitch......15P under your stated conditions isn't a bad place to start. Having a low cost run of the mill aluminum on one engine and a high performance prop on the other, regardless of the pitch differences you are going to get confusing results.

If you don't know where to start, take the engine with the white aluminum 15P prop and use that as a starting point. If that prop puts you where you want to be, get another, same mfgr, same style, same dia. and pitch. Then check the Wide open throttle RPMs of both engines....if close, within a few percent leave it be. If a lot of difference, check the performance of the slower engine....maybe time for some tune up.

 

[racerone]

Maybe run both engines on a marine dyno.----Need to establish power output and see if both engines are in good condition.

 

[gica]

Maybe run both engines on a marine dyno.----Need to establish power output and see if both engines are in good condition.

I am looking into that. One engine runs fine. It's tye one I rebuilt that has the issue in dying in gear in water not on hose or tank but only in gear.
I just sprayed starying fluid and when doing it on the exhaust cover motor goes down at idle and even died once. I assume that is not supposed to happen right?

 

[gica]

First thing is to get loaded up and go out and firewall the throttles and trim to best performance. What is the RPM of both engines under these conditions? Best performance is near the top end of the recommended operational RPM range.....would be somewhere around 5500 to 6000 RPM.
If you are running around 4500 or below you are way over propped....too much pitch......15P under your stated conditions isn't a bad place to start. Having a low cost run of the mill aluminum on one engine and a high performance prop on the other, regardless of the pitch differences you are going to get confusing results.

If you don't know where to start, take the engine with the white aluminum 15P prop and use that as a starting point. If that prop puts you where you want to be, get another, same mfgr, same style, same dia. and pitch. Then check the Wide open throttle RPMs of both engines....if close, within a few percent leave it be. If a lot of difference, check the performance of the slower engine....maybe time for some tune up.

At wot on the lake one goes to 4200 and one 4400 max rpm. I think it os supposed to be 5200. Max speed is 38mph. And yes one of the engines is fully rebuilt but it gives issues in gear on the lake. It dies so I have to raise the idle to max with tye stop screw.
I just sprayed starting fluid and tyebonly area that causes it to bog down was the exhaust area cover. Can that cause RPM to have issues?

 

[racerone]

There is something wrong with that motor !!!

 

[gica]

There is something wrong with that motor !!!

So, I sprayed carb cleaner around the exhaust cover and the engine died. One cover bolt is rusted inside also. Can the exhaust cover cause idle issues? It was replaced when I rebuilt it but I did not put any sealant on the bolts.
Also the plugs on this engine are clean compared to the other one. See the pictures.

 

[Texasmark]

So, I sprayed carb cleaner around the exhaust cover and the engine died. One cover bolt is rusted inside also. Can the exhaust cover cause idle issues? It was replaced when I rebuilt it but I did not put any sealant on the bolts.
Also the plugs on this engine are clean compared to the other one. See the pictures.

A "washed clean" plug (and you are showing 4) can signal water in the combustion chamber....a likely cause.....source, the cooling water that is circulated over the exhaust cover may be getting into your combustion chambers via a defect of some sort with the cover plate between the two areas...and it should be easy to spot with all 4 getting washed.

 

[gica]

A "washed clean" plug (and you are showing 4) can signal water in the combustion chamber....a likely cause.....source, the cooling water that is circulated over the exhaust cover may be getting into your combustion chambers via a defect of some sort with the cover plate between the two areas...and it should be easy to spot with all 4 getting washed.

Thanks TexasMark.
I looked at the pistons and they have carbon build up they don't look steam cleaned clean from water in the chambers.
I was told that with water in the chambers I would show a clean piston, but that is not necessarily true right?
So as I said I did spray carb cleaner over the exhaust cover and it stopped the motor. I did the same on the other motor and it also killed it.
But the plugs on the other motor show carbon build up they are not clean. All 8 plugs were changed at the same time.
My question stands can the clean plugs that we suspect are getting water cause my issue with the motor dying in the water only in gear at idle? Thanks

 

[gica]

A "washed clean" plug (and you are showing 4) can signal water in the combustion chamber....a likely cause.....source, the cooling water that is circulated over the exhaust cover may be getting into your combustion chambers via a defect of some sort with the cover plate between the two areas...and it should be easy to spot with all 4 getting washed.

So I started the motor for 3 min to check the rectifier I just put on that fuxed the 16V over charging the 5 wire one caused. I used the original boack rectangular one and it is back to 13v at idle.
Then I took off tye 4 plugs and took pics of the cylinders with an endo cam.
number 2 and 3 look dry but number 4 looks wet as hell. You tell me if that is normal. Hope you can tell which is which.
I know gravity has a role but this much?

 

[gica]

A "washed clean" plug (and you are showing 4) can signal water in the combustion chamber....a likely cause.....source, the cooling water that is circulated over the exhaust cover may be getting into your combustion chambers via a defect of some sort with the cover plate between the two areas...and it should be easy to spot with all 4 getting washed.

I removed the exhaust cover and I believe there was some water leaking in the exhaust chamber. I took pictures. This should cause my issue right? Only 3 and 4 show milky stuff. I have to also buy tyhe separation plate. The one I reused is way too deformed.
Do I remove the head?

 

[racerone]

The one piston is scored.----Was it like that when you put it in?-----If water got on bearings you have to get this resolved ----ASAP---if not sooner.

 

[gica]

The one piston is scored.----Was it like that when you put it in?-----If water got on bearings you have to get this resolved ----ASAP---if not sooner.

It's a brand new piston. Where do you see the scoring? I will remove the head and clean it all up. Yes I removed everything I will spray some stuff to lube the bearings.

 

[racerone]

??---First picture and 3rd picture.----Some will argue , but I see scoring on the piston !

 

[QBhoy]

At the risk of being mr pessimist…first thing I’d do, is rule out the likelihood of anything nasty, by doing a compression test on the engines. Hate to say it…but those things have a nasty habit of not holding together too well..out with the exceptional few examples that have been meticulously maintained from day one. They don’t suffer neglect or abuse with the same manner that your average 2 stroke of the era might otherwise.
Just maybe rule the chance of it out first off. Then take things from there with regards to props and such like.
Good luck.

 

[gica]

At the risk of being mr pessimist…first thing I’d do, is rule out the likelihood of anything nasty, by doing a compression test on the engines. Hate to say it…but those things have a nasty habit of not holding together too well..out with the exceptional few examples that have been meticulously maintained from day one. They don’t suffer neglect or abuse with the same manner that your average 2 stroke of the era might otherwise.
Just maybe rule the chance of it out first off. Then take things from there with regards to props and such like.
Good luck.

Compression was done 140 and 135.
I mentioned earlier in the thread. Motor was rebuilt completely. I have several posts here with all the work.
I just measured the worp clearance of the exhaust cover and it was .018in
I used a stone to bring it straight and now is at 002 in. Pretty close to straight. I don't know the specs on the warp allowed.
But it should be better. No wonder there was water.
The head has .004 or less diagonally.
I have to look at the specs.

 

[QBhoy]

Compression was done 140 and 135.
I mentioned earlier in the thread. Motor was rebuilt completely. I have several posts here with all the work.
I just measured the worp clearance of the exhaust cover and it was .018in
I used a stone to bring it straight and now is at 002 in. Pretty close to straight. I don't know the specs on the warp allowed.
But it should be better. No wonder there was water.
The head has .004 or less diagonally.
I have to look at the specs.

Fair play. If that compression is accurate, it’s a fairly lofty set of figures for sure. Best of luck.

 

[gica]

Yeah it was a long project, I knew about the bad rep Force engines got. I have a friend with a 96 125, runs great offshore.
This one is a 1990 and 34 years later you can rebuild it for 1k and maybe run it another 10 years for offshore fishing.
Spending 10k on a used engine right now is not something I wanna do. I would rather buy a new boat and finance it.
This one has twin Force. I like tinkering.
Bad vice.

 

[Texasmark]

Since you said that water was definitely getting into the exhaust chamber then I would think as each piston went up and down it could introduce water into that cylinder. The water comes in under force from the water pump so I can rationalize this. On the one piston being wet and the others dry, possibly that one was ready to fire (wet) but didn't due to engine timing not ready for that cylinder to fire when you stopped it.

Compression is fine with me. On the water getting into the bearings, that surely would be something that needed to be addressed immediately. I don't know how to address the how to on that problem, never had it. Maybe one of the guys that answered and know how to fix that problem can direct you.